Fitness of Encarsia sophia （Hymenoptera： Aphelinidae） parasitizing Trialeurodes vaporariorum and Bemisia tabaci （Hemiptera： Aleyrodidae）

Fitness and efficacy of Encarsia sophia （Girault ＆ Dodd） （Hymenoptera： Aphelinidae） as a biological control agent was compared on two species of whitefly （Hemiptera： Aleyrodidae） hosts, the relatively smaller sweetpotato whitefly, Bemisia tabaci （Gennadius） biotype ＇B＇, and the larger greenhouse whitefly, Trialeurodes vaporariorum （Westwood）. Significant differences were observed on green bean （Phaseolus vulgaris L.） in the laboratory at 27 ± 2℃, 55% 4- 5% RH, and a photoperiod of 14 ： 10 h （L ： D）. Adult parasitoids emerging from T. vaporariorum were larger than those emerging from B. tabaci, and almost all biological parameters of E. sophia parasitizing the larger host species were superior except for the developmental times of the parasitoids that were similar when para- sitizing the two host species. Furthermore, parasitoids emerging from T. vaporariorum parasitized more of these hosts than did parasitoids emerging from B. tabaci. We conclude that E. sophia reared from larger hosts had better fitness than from smaller hosts. Those from either host also preferred the larger host for oviposition but were just as effective on smaller hosts. Therefore, larger hosts tended to produce better parasitoids than smaller hosts.

Inundative field releases and evaluation of three predators for Bemisia tabaci （Hemiptera： Aleyrodidae） management in three vegetable crops

The sweetpotato whitefly, Bemisia tabaci （Gennadius） （Hemiptera： Aleyrodidae）, is a global pest on numerous crops, including vegetables. Weekly inundative releases of a coccinellid predator （Coccinella undecimpunctata L. [Coleoptera： Coccinellidae]）, a common green lacewing predator （Chrysoperla carnea Stephen [Neuroptera： Chrysopidae]）, and a mirid predator （Macrolophus caliginosus [Wagner] [Hemiptera： Miridae]） were independently made in three vegetable crops （cabbage [Brassica oleracea var. capitata L.], cucumber [Cucumis sativus L.], and squash [Cucurbita pepo L.]） for the management of the sweetpotato whitefly. Approximately 1 million to 2.5 million larvae or nymphs of each predator were released in the vegetable crops during 20 weeks. Whitefly populations were reduced by ≈ 25%-45% during most of the season in each crop where each predator was released. The effect of each predator was similar on whitefly population reduction. Late in the season （October） when whitefly populations were low, generally no benefit was obtained from releasing the predators. Numbers of predators recovered during sampling in all crops were greatest for C. carnea, but this corresponded with the fact that more individuals of this predator were released than any other predator in the experiment. These results help define the utility of these natural enemies for managing B. tabaci in vegetable crops.

Population suppression of Bemisia tabaci （Hemiptera： Aleyrodidae） using yellow sticky traps and Eretmocerus nr. rajasthanicus （Hymenoptera： Aphelinidae） on tomato plants in greenhouses

We conducted three experiments for management of Bemisia tabaci （Gennadius） biotype＇ B＇ on tomatoes under greenhouse conditions： （i） vertically placing yellow sticky cards either parallel or perpendicular to tomato rows at a rate of 1 per 3-m row; （ii） releasing Eretmocerus sp. nr. rajasthanicus once at 30 adults/m2 in the high whitefly density greenhouses （〉 10 adults/plant）, or twice at 15 adults/m2 at a 5-day interval in the low whitefly density greenhouses （〈 10 adults/plant）; and （iii） using combinations of yellow sticky cards that were placed vertically parallel to tomato rows and parasitoids released once at 30/m2 in high whitefly density greenhouses or twice at 15/m2 at a 5-day interval in low whitefly density greenhouses. Our data show that yellow sticky cards trapped B. tabaci adults and significantly reduced whitefly populations on tomato. The yellow sticky cards that were placed parallel to tomato rows caught significantly more whitefly adults than those placed perpendicular to tomato rows on every sampling date. In the treatment where parasitoids were released once at 30/m2 in high whitefly density greenhouses, the number of live whitefly nymphs were reduced from 4.6/leaf to 2.9/leaf in 40 days as compared with those on untreated plants on which live whitefly nymphs increased from 4.4/leaf to 8.9/leaf. In the treatment where parasitoids were released twice at 15/m2 in low whitefly density greenhouses, the numbers of live nymphs ofB. tabaci on tomato leaves were reduced from 2.1/leaf to 1.7/leaf in 20 days as compared with those on untreated plants on which numbers of live nymphs ofB. tabaci increased from 2.2/leaf to 4.5/leaf. In the treatment of yellow sticky cards and parasitoid release once at 30/m2 in high whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 7.2/leaf to 1.9/leaf, and in the treatment of yellow sticky cards and parasitoid release twice at 15/m2 at a 5-day interval at low whitefly density, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.5/leaf to 0.8/leaf; whereas the numbers of live nymphs of B. tabaci on untreated plants increased from 4.4/leaf to 8.9/leaf. An integrated program for management of B. tabaci on greenhouse vegetables by using yellow sticky cards, parasitoids and biorational insecticides is discussed.